State Key Laboratory of High Field Laser Physics

A series of layered molybdenum dichalcogenides, i.e., MoX₂ (X = S, Se and Te), were prepared in cyclohexyl pyrrolidinone by a liquid-phase exfoliation technique. The high quality of the two-dimensional nanostructures was verified by transmission electron microscopy and absorption spectroscopy. Open- and closed-aperture Z-scans were employed to study the nonlinear absorption and nonlinear refraction of the MoX₂ dispersions, respectively. All the three-layered nanostructures exhibit prominent ultrafast saturable absorption (SA) for both femtosecond (fs) and picosecond (ps) laser pulses over a broad wavelength range from the visible to the near infrared. While the dispersions treated with low-speed centrifugation (1500 rpm) have an SA response, and the MoS₂ and MoSe₂ dispersions after higher speed centrifugation (10,000 rpm) possess two-photon absorption for fs pulses at 1030 nm, which is due to the significant reduction of the average thickness of the nanosheets; hence, the broadening of band gap. In addition, all dispersions show obvious nonlinear self-defocusing for ps pulses at both 1064 nm and 532 nm, resulting from the thermally-induced nonlinear refractive index. The versatile ultrafast nonlinear properties imply a huge potential of the layered MoX2 semiconductors in the development of nanophotonic devices, such as mode-lockers, optical limiters, optical switches, etc.

Ti₃C₂T_x based flexible temperature sensors exhibit a tunable high performance and realize proximity and illumination detection for electronic skin.

A physically transient non-volatile memory device made of keratin exhibits great resistive switching performance.

Wafer-scale neat MoS₂ optical thin films were fabricated successfully, and they show a superior broadband ultrafast saturable absorption performance.

through efficient energy transfer from the nanoparticle to the photosensitizer, which can efficiently damage cancer cells. In addition to their UV-excited luminescence, PLNPs also exhibited a long-lasting luminescence afterglow. Thus, PLNPs can serve as a persistent light source for PDT activation after excitation by an external light source is stopped. When fractionated light was used for excitation instead of continuous light at equivalent irradiation doses, confocal microscopy revealed that the photosensitizer-conjugated PLNPs showed a significantly enhanced cancer cell killing ability. Moreover, quantitative flow cytometry showed that fractionated light irradiation (60 s/100 s on/off cycle) produced up to ten times more cancer cell apoptosis/necrosis than the same dose of continuous light irradiation did. These results indicate that photosensitizer-conjugated PLNPs combined with fractionated irradiation show good potential for low-dose UV-mediated PDT activation.

Correction for 'Direct synthesis of large-scale hierarchical MoS2 films nanostructured with orthogonally oriented vertically and horizontally aligned layers' by Xiaoyan Zhang et al., Nanoscale, 2016, DOI: 10.1039/c5nr05938k.

The triggering of wave-breaking in a three-dimensional laser plasma wake (bubble) is investigated. The Coulomb potential from a nanowire is used to disturb the wake field to initialize the wave-breaking. The electron acceleration becomes more stable and the laser power needed for self-trapping is lowered. Three-dimensional particle-in-cell simulations were performed. Electrons with a charge of about 100pC can be accelerated stably to energy about 170MeV with a laser energy of 460mJ. The first step towards tailoring the electron beam properties such as the energy, energy spread, and charge is discussed.

High-energy tens (10s) to hundreds (100s) petawatt (PW) lasers are key tools for exploring frontier fundamental researches such as strong-field quantum electrodynamics (QED), and the generation of positron-electron pair from vacuum. Recently, pulse compressor became the main obstacle on achieving higher peak power due to the limitation of damage threshold and size of diffraction gratings. Here, we propose a feasible multistep pulse compressor (MPC) to increase the maximum bearable input and output pulse energies through modifying their spatiotemporal properties. Typically, the new MPC including a prism pair for pre-compression, a four-grating compressor (FGC) for main compression, and a spatiotemporal focusing based self-compressor for post-compression. The prism pair can induce spatial dispersion to smooth and enlarge the laser beam, which increase the maximum input and output pulse energies. As a result, as high as 100 PW laser with single beam or more than 150 PW through combining two beams can be obtained by using MPC and current available optics. This new optical design will simplify the compressor, improve the stability, and save expensive gratings/optics simultaneously. Theoretically, the output pulse energy can be increased by about 4 times using the MPC method in comparison to a typical FGC. Together with the multi-beam tiled-aperture combining method, the proposed tiled-grating based tiled-aperture method, larger gratings, or negative chirp pulse based self-compression method, several 100s PW laser beam is expected to be obtained by using this MPC method in the future, which will further extend the ultra-intense laser physics research fields.

Control of multiple filamentation by laser-induced microlens effect due to a nonlinear interaction of two overlapping laser beams inside a glass plate was demonstrated. Individual or multiple spots on the white light pattern which is a product of multiple filamentation through a mesh can be switched on and off with a very high contrast ratio on a femtosecond time scale. This phenomenon can find applications such as ultrafast optical switch and high-speed sampling.

This letter demonstrates an alternative method to form gallium silicate glass ceramics using high-energy electron irradiation. Compared with glass ceramics obtained from the conventional thermal treatment method, the distribution and crystal sizes of the precipitated Ga2O3 nanoparticles are the same. An advantage of this method is that the spatial distribution of the precipitated nanoparticles can be easily controlled. However, optically active dopants Ni2+ ions do not participate in the precipitation during electron irradiation.

PET–folic acid coated carbon nanodots (CDots) as the targeting fluorescence imaging probe agents. Folic acid (FA) was used as the targeting ligand to enhance the CDots' binding capability and penetration into the target cancer cells.

Recent years have witnessed significant progress in the field of two-photon-activated photodynamic therapy (TP-PDT). However, traditional photosensitizer (PS)-based TP-PDT remains a critical challenge in clinics due to its low two-photon absorption cross sections. Here, we propose that the therapeutic activity of the current photosensitizer, sulfonated Al-phthalocyanine (AlPcS), can be efficiently excited via plasmonic-resonance energy transfer from the two-photon excited gold nanobipyramids (GBPs) and further generates cytotoxic singlet oxygen for cancer eradication. GBPs possess large two-photon absorption cross sections, excellent photostability, and biocompatibility, which can be used for a high two-photon light-harvesting material in biomedical applications. We compared the in vitro and in vivo capabilities of AlPcS-loaded GBPs as a TP-PDT agent for theranostic applications by benchmarking them against those of the extensively studied gold nanospheres (GNS) and nanorods (GNR). Although all these Au nanostructures could cause enhanced PS two-photon excitation fluorescence and improved singlet oxygen generation capability via the plasmonic resonance-energy transfer process, GBP-AlPcS exhibited the highest two-photon efficiency for photodynamic therapy. Remarkably, in vivo experiment results clearly indicated that the GBP-AlPcS caused efficient suppression of tumor growth and minimal adverse effects on orthotopic A549 human lung tumor xenografts. The system presents great efficiency in improving the treatment depth and precision of traditional photodynamic therapy.

An electron with an appropriate initial velocity injected into an oncoming, ultraintense circularly polarized laser pulse can execute a circular relativistic motion at the peak of the laser pulse. The circulating electron then radiates in the same manner as that in the storage ring of a conventional synchrotron source. Owing to the extremely small orbit radius, the laser-field synchrotron radiation thus generated can be a compact source of radiation pulses at short wavelength and short duration.

We propose a metallic nanostructure consisting of a nanodisk in a nanocrescent. At the quadrupole plasmon resonance wavelengths of the nanocrescent/nanodisk structures, the local electric field amplitudes at the crescent tips are 15 times higher than those of the single nanocrescents. In addition, the quadrupole resonance wavelengths are tunable in the visible region while the peak widths keep less than 5 nm. We study the mechanisms of the local field enhancement (LFE), and find that the coupling between the quadrupole resonance modes of the nanogap and the nanocrescent result into the high LFE factor.

Employing a novel front-end based on femtosecond noncollinear optical-parametric amplification and second-harmonic generation processes in a Ti:sapphire chirped pulse amplification laser system, we first demonstrate the efficient enhancement of amplified spontaneous emission (ASE) contrast. Cleaned seed pulses of 100-μJ energy generated by the front-end are amplified to 0.75 J before compressor. After compression and under pulse peak power of 7 TW, the ASE contrast is promoted from original ~ 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> to ~ 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> . The experimental results for nanometer film target interactions also demonstrate the improvement of the contrast. Finally, the evolution of the ASE contrast under different seed pulse energy is demonstrated experimentally, which can be used to design the higher power laser with higher ASE contrast.

We investigated femtosecond laser-filamentation-induced airflow, water condensation and snow formation in a cloud chamber filled respectively with air, argon and helium. The mass of snow induced by laser filaments was found being the maximum when the chamber was filled with argon, followed by air and being the minimum with helium. We also discussed the mechanisms of water condensation in different gases. The results show that filaments with higher laser absorption efficiency, which result in higher plasma density, are beneficial for triggering intense airflow and thus more water condensation and precipitation.

Instabilities in the interaction of a normal intensity circularly polarized pulse and an overdense foil are investigated with two and three dimensional particle-in-cell simulations. Two typical instabilities were shown during the interaction. One is the Weibel-like instability induced by the current far above the Alfven limit, and the other is the boundary instability with ring structures spreading to the center from the boundary which is induced by the transverse boundaries of the target or the laser pulse. These instabilities are important to the proton acceleration by using moderate laser pulses at intensities accessible experimentally with existing laser systems.

The influence of focus spot and target thickness on multi-keV x-ray sources generated by 2ns duration laser heated solid targets are investigated on the Shenguang II laser facility. In the case of thick-foil targets, the experimental data and theoretical analysis show that the emission volume of the x-ray sources is sensitive to the laser focus spot and proportional to the 3 power of the focus spot size. The steady x-ray flux is proportional to the 5∕3 power of the focus spot size of the given laser beam in our experimental condition. In the case of thin-foil targets, experimental data show that there is an optimal foil thickness corresponding to the given laser parameters. With the given laser beam, the optimal thin-foil thickness is proportional to the −2∕3 power of the focus spot size, and the optimal x-ray energy of thin foil is independent of focus spot size.

We demonstrate the measurement of field-free molecular alignment of air can be realized by combining the weak field polarization technique (WFPT) with a balanced detection system. The measured signal is proportional to the alignment parameter. Periodic revival structures of the transient alignment and permanent alignment between revivals can be detected clearly by a single measurement with high sensitivity. Fourier transform spectrum of the measured signal agrees well with the calculation result and provides information of the populations of different J states in the rotational wave packet.

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, we report the room temperature spectroscopic and thermal properties and continuous-wave (CW) laser operation of a new <formula formulatype="inline"> <tex Notation="TeX">${\hbox {Yb}}{:}{\hbox{CaNb}}_{2}{\hbox{O}}_{6}$</tex> </formula> crystal. The peak absorption cross section for the <formula formulatype="inline"> <tex Notation="TeX">${\rm E}\Vert{\rm a}$</tex></formula> polarization is <formula formulatype="inline"><tex Notation="TeX">$0.97\times 10^{-20}\ {\hbox {cm}}^{2}$</tex> </formula> with a full-width at half-maximum of 28 nm at 975 nm. The stimulated emission cross section is <formula formulatype="inline"><tex Notation="TeX">$1.19\times 10^{-20}\ {\hbox {cm}}^{2}$</tex></formula> at 1062 nm. The thermal conductivities at room temperature are 5.40, 5.15, and 6.05 <formula formulatype="inline"> <tex Notation="TeX">${\rm Wm}^{-1}{\rm K}^{-1}$</tex></formula> along the <emphasis emphasistype="italic">a</emphasis>-, <emphasis emphasistype="italic">b</emphasis>-, and <emphasis emphasistype="italic">c</emphasis>-axis, respectively. The fracture strength of <formula formulatype="inline"><tex Notation="TeX">${\hbox {Yb}}{:}{\hbox{CaNb}}_{2}{\hbox{O}}_{6}$</tex> </formula> single crystal is 315 MPa. The properties of <formula formulatype="inline"> <tex Notation="TeX">${\hbox {Yb}}{:}{\hbox{CaNb}}_{2}{\hbox{O}}_{6}$</tex> </formula> crystal were compared with those of typical Yb-doped materials. A CW output power of 801 mW at 1062 nm was obtained with a slope efficiency of 19% by use of diode pumping. </para>